I would also add that Thorin being exiled does not mean he was homeless. He might have had to work harder at least initially than he would have expected to do if he'd remained in the Lonely Mountain, but he obviously was not in poverty when he arrived at Bag End. His clothing was rich and he had a golden harp.

I find it difficult to imagine him as grizzled and careworn as if being exiled led to a nomadic, tramp-like existence where every year was firmly etched on his face. There was an obvious lack of real preparation - mental or practical - for the realities of the quest, or at least the sheer slog of the journey there, where they could expect to live rough for much of the time. This is itself evidence that they were living fairly comfortably, if not at the level that Thorin took as his due.

So he might have been haggard in appearance, but there is no indication that he was within the book. Whereas the book did stress leadership, fighting skills, courage, together with pride, arrogance, and a sense of (rightful) entitllement to his lost inheritance. Those qualities appear to be the ones PJ is highlighting, and from this picture RA can be easily identified as the one with mission and the driving force amongst the motley dwarven crew.

Also I do like the way that PJ has subverted the standard Knights of the Round Table quest with this ragtag bunch of dwarves, plus one hobbit and a wandering wizard.